Wicking apparatus

ABSTRACT

Apparatus for lubricating the heated fuser roll in a heated pressure xerographic fusing system. The apparatus includes an applicator roll for providing a film of oil to a wick assembly having a Teflon layer contacting the fuser roll and a Nomex layer contacting the applicator roll where the Nomex layer is flame treated to provide high oil retention and prevent binding the drive of the applicator roll.

[111 3,745,972 [451 July 17, 1973 United States Patent [1 1 Thettu3,379,171 4/1968 Cordingly ct a1. 118/261 2,909,150 10/1959Ungercr..................... 118/227 2,754,752 7/1956 Robinson et101/1325 [54] WICKING APPARATUS [75] Inventor: Raghulinga R. Thettu,Webster,

[73] Assignee: Xerox Corporation, Stamford 22 Filed:

, Conn. Primary Examiner-Mervin Stein July 20 1971 AssistantExaminer-Leo Millstein Attorney-James J. Ralabate, Melvin A. Klein etal.

21 Appl. No.: 164,370

[57] ABSTRACT Apparatus for lubricating the heated fuser roll in a [52]US. ll8/26l, 1l8/60, 118/268 [51] Int. B05c 11/00 heated pressurexerographic fusing system. The apparatus includes an applicator roll forproviding a film of oil to a wick assembly having a Teflon layercontacting the fuser roll and a Nomex layer contacting the applica- 3 2in D is 6 12 W i w 2 m2 6 "2 ml 6 m2 m0 6 b2 c/ r00 .1 1 I 0 d i Q i F 100 5 I [56] References Cited UNITED STATES PATENTS tor roll where theNomex layer is flame treated to provide high oil retention and preventbinding the drive of s e r u .m F g .m W a r n s s m a mm a mm M ma 3"im t.m 0 0 GSB 320 676 999 111 ll] 85 2000 39 027 83 332 PArsmwm v I 13.745.972

' SHEEI 1 0F 3 INVENTOR. V RAGHULINGA R. THETTU ATTORACV v Pmmmm 1 1 mSHEEIEOFS FIG. 2

'PATENTED U 1 7 sum 3 or 3 FIG. 4 b

FIG. 4a

WICKING APPARATUS This application relates to fusing systems and inparticular to an improved lubricating apparatus for removing tonerparticles from the fuser roll of a heated pressure fusing system.

In the practice of xerography as described in U.S. Pat. No. 2,297,691 toChester F. Carlson, a xerographic surface comprising a layer ofphotoconductive insulating material affixed to a conductive backing isused to support electrostatic images. In the usual method of carryingout the process, the xerographic surface is electrostatically chargeduniformily over its surface and then exposed to a light pattern of theimage being reproduced to thereby discharge the charge in the areaswhere the light strikes the layer. The undischarged areas of the layerthus form an electrostatic charge pattern in conformity with theconfiguration of the orginal light pattern.

The latent electrostatic image can then be developed by contacting itwith a finely divided electrostatically attractable material such as apowder. The powder is held in image areas by the electrostatic chargeson the layer. Where the charge field is greatest, the greatest amount ofpowder is deposited; where the charge field is least, little or nomaterial is deposited. Thus, a powder image is produced in conformitywith the light image of the document or object being reproduced. Thepowder is subsequently transferred to a sheet of paper or other surfaceand suitably affixed thereto to form a permanent print.

One typical device for fixing the toner particles to the backing sheetis by a heated pressure fuser roll system in which the copy sheet ispassed through the nip of a Teflon coated heated fuser roll and a backuproll as described in US. Pat. Nos. 3,256,002 and 3,268,351. In suchfusing systems, care must be taken to remove unwanted toner particlesfrom the heated fuser roll prior to its contact with the copy beingfused. If care is not taken to keep the fuser roll free of tonerparticles, these toner particles can build up on the face of the fuserroll and degrade the quality of the for by removing the fusingproperties on the surface of the roll contacting the copy sheet andtoner images. Furthermore, such unwanted toner particles can be releasedfrom the fusing roll upon its subsequent contact with the toner image tofuse toner particles to the copy sheet in non-imaged areas. A wick isgenerally used to dispense silicone oil by gravity on the externalTeflon surface of the heated fuser roll by a pad overlying the heatedfuser roll.

While the gravity dispensing wick which is in pad form is satisfactorywhere the wick is elevated over the nip, it is not altogethersatisfactory in other arrangements, such as, where the heated fuser rollis disposed as the bottom roll of the fusing system.

It is therefore an object of the present invention to improve heatedpressure fusing systems.

It is another object of the present invention to improve wickingassemblies of high temperature stability for use with heated pressurefusing systems.

It is another object of the invention to provide wicking assembliescapable of retaining oil over a long shutdown period against gravity.

It is still another object of the present invention to enhance thewicking properties of an oil applicator wick.

It is still another object of the present invention to provide animproved wicking assembly which is compatible with silicone oil andconforms to objects.

It is still another object of the invention to provide a wick assemblywhich eliminates substantially stalling of an oil applicator contactingthe wick.

It is still another object of the present invention to minimizeunnecessary maintenance of copier/duplicator systems.

These and other objects of the instant invention are obtained by a newand improved wicking assembly which comprises two different layers ofmaterials, Teflon and Nomex, in which the Teflon material contacts theheated fuser roll and the Nomex material is in contact with the oilapplictor roll and has been flame treated to form a smooth fuzz freesurface such that sufficient oil is retained at all times by the wickassembly for dispensing to the heated fuser roll.

Further objects of this invention together with additional features andadvantages thereof will become apparent from the following detaileddescription of the embodiment of the invention when read in conjunctionwith the accompanying drawings wherein:

FIG. 1 is a schematic representation of an automatic xerographicreproducing machine incorporating a heated pressure fusing systemutilizing the improved wicking assembly of the present invention;

FIG. 2 is a side elevational view of the heated pressure fusing system;

FIG. 3 is an isometric view of the improved wicking assembly accordingto the present invention;

FIG. 4 a is an exploded view of a prior art wick surface; and

FIG. 4 b is an exploded view of the flame treated fuzz free surface ofthe present invention.

Referring now to the drawing as shown in FIG. 1 an embodiment of theinvention in a suitable environment such as an automatic xerographicreproducing machine. The automatic xerographic reproducing machineincludes a xerographic plate or surface 10 formed in the shape of adrum. The plate has a photoconductive layer or light receiving surfaceon a conduc tive backing joumaled in a frame to rotate in a directionindicated by the arrow. The rotation will cause the plate surface tosequentially pass a series of xerographic processing stations.

For purposes of the present disclosure the several xerographicprocessing stations in the path of movement of the plate surface may bedescribed functionally as follows:

a charging station A which the uniform electrostatic charge is depositedonto the photoconductive plate;

an exposure station B at which light or radiation pattern of copies tobe reproduced is projected onto the plate surface to dissipate thecharge in the exposed areas thereof to thereby form a latentelectrostatic image of the copies to be reproduced;

a developing station C at which xerographic developing materialincluding toner particles have an electrostatic charge opposite to thatof the latent electrostatic image is cascaded over the latentelectrostatic image to form a powdered image in configuration of thecopy being reproduced;

a transfer station 0 which the powdered image is electrostaticallytransferred from the plate surface to a transfer material such as paperwhich is then passed through heated pressure fusing system according tothe present invention as will be described hereinafter; and

a drum cleaning and discharge station E at which the plate surface isbrushed to remove residual toner parti cles remaining thereon afterimage transfer and at which the plate is exposed to a relatively brightlight source to effect substantially complete discharge of any residualelectrostatic charge remaining thereon.

For further details of the xerographic processing stations, abovereference is made to copending application Ser. No. 838,902 filed July3, 1969.

Referring now in particular to FIG. 2 there is shown the heated pressurefusing system of the present invention which includes a heated fuserroll 16 and a backup pressure roll 18. Fuser roll 16 is a hollowcircular cylinder with a metallic core 20 and a Teflon layer 22. Aquartz lamp 24 serves as a source of thermal energy and is located atthe center of the fuser roll. Power to the lamp is controlled by athermal sensor generally called a thermister contacting the periphery ofthe fuser roll as described, for example, in US. Pat. No. 3,357,249. Thebackup roll 18 is also circular cylinder and is made up of a metal core30 surrounded by a thick rubber layer 32 and also a Teflon layer 34 toprevent soaking silicone oil into rubber layer 32 and subsequentswelling.

When the two rollers 16 and 18 are engaged as shown in FIG. 2 theapplied load deforms the rubber in the pressure roll to provide the nipwith a finite width. The copy sheet 40 electrostatically bearing thetoner images 42 on the underside is brought into contact with the nip ofthe rolls with the toner image contacting the fuser roll 16, For a giventemperature of the fuser roll, the fusing rate will depend upon thecontact arc length of the support material against the dwell time, i.e.,the time the toner images remain between the fuser roll 16 and thebackup roll 18. Dwell time can be varied either by changing the surfacevelocity of the rolls or by varying the contact arc length and holdingthe speed of the roll the same. Contact arc length depends on thesoftness of the rubber on backup roll 18 and on the amount of pressurebetween the rolls l6 and 18. The mechanism for driving the rolls and forlowering and raising the rolls into contact can be accomplished by anysuitable means as that described, for example, in US. Pat. No. 3,291,466or by a suitable mechanical camming device.

As a sheet of material is advanced between the rolls l6 and 18 the tonerimages on the support material will contact the peripheral heatedsurface of the roll 16 whereby the toner images become tackified and inthis tackified condition the toner will tend to offset on this rollexcept that it is partially prevented from doing so by the Tefloncoating on the roll. However, it is by the wicking apparatus of thepresent invention which is successful in applying a thin film of offsetpreventing liquid such as silicone oil to the Teflon surface 22 of thefuser roll 16 such that toner offset is prevented as will be describedhereinafter.

An oil dispensing apparatus 45 includes wicking assembly 48, an oil pan50 for maintaining a supply of silicone oil 51 and an applicator roll52. The oil pan is loaded against the heated fuser roll 16 by a springaction mounting (not shown) as details of the mounting form no part ofthe present invention. Applicator roll 52 is used to convey a thin filmof oil to the bottom face 55 of the wicking assembly as the applicatorroll is rotated in the direction shown by the arrow. Desirably,

the applicator roll 52 is driven by an oil dispensing motor 58 which isenergized during the fusing operation for a period depending upon thenumber of copies being produced.

In accordance with the present invention, the wicking assembly 48includes two different layers of wicking materials. One layer 62 is madeof Teflon which contacts the surface of the heated fuser roll 16.Another layer 64 is made of Nomex which has its underside 55 in contactwith the applicator roll 52. Both Teflon and Nomex are trademarks ofDuPont Company, of Wilmington, Delaware. Layers 62 and 64 are assembledin overlapping relationship and their ends are clamped between plates 66and 68 which are secured by any suitable means such as screws 70 as bestshown in FIG. 3. Spring metal brackets 72 and 74 serve to providesupport and conforming characteristics to the fuser roll for the wickingassembly. Tab portions 75 and 76 are provided for facilitating thehandling of the wicking assembly for insertion and removal of theassembly into and out of the fusing system. Teflon is used as the upperlayer because it has high lubricating characteristics as well as thermalstability at elevated temperatures ranging up to 400 F and above. Nomexis used as the lower layer because of the thermal stability at elevatedtemperatures up to 400 F and above and due to its high oil retentioncharacteristics. Also both Teflon and Nomex are non-combustiblematerials.

The oil applicator apparatus utilizes an auxiliary wick 75 which may bemade out of any suitable wicking material. Suitable materials are Nomexand Dacron. Preferably the auxiliary wick material is able to withstandhigh temperatures, as high as 400 F. The auxiliary wick is arranged sothat it is touching the applicator roll in close proximity to thewicking assembly and is secured in place by a support member 77 and aholding member 80 located adjacent to the bottom of the oil pan. Theauxiliary wick 75 serves to bring the oil up to the applicator roll to alevel such that upon rotation of the roll during one-half of one copytime the oil contacts the wick assembly. It has been found thatauxiliary wick is useful especially during a short run operation whenrotation of the applicator roll is small and the oil must be supplied tothe wick assembly to equalize the difi'erential supplied during a muchlonger run. Thus, in the case of a long run, the oil will be primarilysupplied by the applicator roll due to a lag in the capillary action ofthe auxiliary wick.

In order to enhance the oil retention characteristics of wickingassembly 48 and also enable trouble free application of oil to thesurface of the Nomex layer 64, the lower surface 55 is flame treated toburn all the loose fibers or fuzz to render a substantially smoothmembrane-like surface free of loose fibers as best shown in FIG. 4 b.Burning should be sufficient to form the surface fibers into a porousmembrane finished pattern. It has been found that removal of thesefibers from the Nomex layer has enabled a high oil retention of thelayer while insuring that the applicator roll does not stall which isnormally the case where the layer is dry which is caused by oil leakingthrough loose fiber material or fuzz. Since the applicator roll motor isdesirably of a low power unit, it is essential that there be no bindingbetween the Nomex layer and the applicator roll causing the motor tostall. It has been observed that with the fuzz and/or loose fibersremoved that motor stalling is prevented and high oil retentionqualities retained.

The effect of the membrane-like substantially smooth fuzz-free surfaceacts in the same manner as a one-way valve. More specifically, the oilfilm from the applicator roll surface is transmitted through the flametreated surface on the bottom of the wicking assembly by capillaryaction forces against gravity. Once the oil is in the body of the wickit cannot return to the applicator roll because the membrane-like fuzzfree surface prevents oil droplets from forming on its surface. In thecase of conventional wicks (FIG. 4 a) loose fiber materials or fuzzserve as a basis for oil droplet formation. Since the weight of the oildroplet is greater than the wetting forces of an oil droplet on thefiber material the oil droplet would ordinarily drain off. In the caseof the present invention the draining properties of the wick surface areminimized by the unique wick structure described above. In this manner,the oil retention gradient normally established by the thicknessof thewick layer is minimized because the amount of oil retained throughoutthe layer is uniform irrespective of its thickness.

In the past it has been observed that in heated pressure roll fusingsystemsthat uniform application of oil to the heated fuser roll wasdifficult to achieve because of an excessive lag in the capillaryactionfrom the bottom to the top of the wicking assembly. By the presentinvention, the lag is minimized due tothe improved oil retainingproperties of the substantially smooth membrane-like fuzz free surfacecontacting the oil applicator roll.

While the instant invention as to :its object and advantages has beendescribed as being carried in a specific embodiment thereof it is notintended to be limited thereby but it is intended to be covered broadlywithin the scope of the appended claims.

What is claimed is:

1. In a heated pressure roll fusing system for fusing toner images ofelectrostatic copying machine and in which a heated fuser roll disposedbelow the copy path is coated with an oil to prevent toner offset, animproved wicking apparatus comprising an applicator roll for dispensingoil onto the lower surface of a wick assembly when copies are beingprocessed, a wick assembly positioned between the applicator roll and aheated fuser roll including a top layer and a lower layer,

said lower layer having the lower surface thereof flame treated toestablish a substantially smooth membrane-like fuzz free area to retainoil over a sufficiently long period when the dispensing roll isinoperative.

2. Apparatus according to claim I wherein said layers are clampedtogether by retaining members to form a unitary assembly.

3. Apparatus according to claim 2 wherein the unitary assembly has tabmembers extending therefrom to facilitate handling thereof.

4. Apparatus according to claim 2 wherein said top layer is made ofTeflon and said lower layer is made of Nomex.

2. Apparatus according to claim 1 wherein said layers are clampedtogether by retaining members to form a unitary assembly.
 3. Apparatusaccording to claim 2 wherein the unitary assembly has tab membersextending therefrom to facilitate handling thereof.
 4. Apparatusaccording to claim 2 wherein said top layer is made of Teflon and saidlower layer is made of Nomex.